gas filled creatures with jet propulsion....
Oh I get it. They jet fart their way through the atmosphere.
In a sense yeah. In the book they took air in one end while straining out bits of food and expelled the air out the other.
Robert Forward fiction was always good because he was a practical physicist. He did some speculative physics work but was very reserved and only wanted to work on things we would be capable now of the fairly near future. He was also a strong advocate of free market space and co founded Tethers unlimited which is used by various space agencies today.